There is no admission that the background art disclosed in this section legally constitutes prior art.
Carbon nanotubes (CNTs) have attracted significant interest in recent years because of their extraordinary mechanical, electrical and thermal properties. Typically, carbon nanotubes have a diameter of about 10 nm to about 100 nm. Radushlevich and Lukyanovich (Carbon, 2006, Vol. 44, 1621-1623) were the first group to clearly image 50 nanometer diameter carbon tubes. Later work by Oberlin, Endo, and Koyama (J. Cryst. Growth, 1976, Vol. 32, 335) showed that hollow carbon fibers with nanometer-scale diameters could be produced using a vapor-growth technique. Subsequent work by Iijima (Nature, 1991, Vol. 354, 56-58) showed that carbon nanotubes (CNTs) were produced in arc-burned carbon rods and this work has fostered continued interest from research groups and industry in CNTs because of their remarkable electrical, mechanical, and thermal properties and their potential for a variety of applications. CNTs are unique tubular structures of nanometer diameter and may consist of one wall (single-walled nanotubes, SWNTs) to several, and up to hundreds (multi-walled nanotubes, MWNTs) of concentric carbon shells. Their molecular structure is closely related to the hexagonal arrangement of carbon atoms in graphite sheets. Carbon nanotubes have been prepared by employing a variety of strategies such as chemical vapor deposition (CVD) (Appl. Phys. Lett., 1993, Vol. 62, 202-204), arc-discharge (Nature, 1991, Vol. 354, 56-58), and laser-ablation (Chemical Physics Letters, 1995, Vol. 243, 49-54); the last two methods involving the ablation of a carbon source allow the carbon to be redeposited in tubular form. Although considerable effort has been made to improve the techniques for carbon nanotube production, there are still many problems that prevent the manufacturing of large volumes of carbon nanotubes in a controlled manner. Extremely high temperatures, complicated controls, difficult purification processes, and very low yields currently have made it too expensive for production of the bulk quantities of carbon nanotubes that would be required for large-scale structural applications.
There is a growing interest in the development of new carbon materials directly from plant materials to make carbon composites (Carbon, 1997, Vol. 35, 259-266; 45th International SAMPE, 2000), carbide ceramics (Holzforschung, 2003, Vol. 57, 440-446; J. of the European Ceramic Society, 2004, Vol. 24, 495-506; Carbon, 2005, Vol. 43, 1174-1183), and environmental sorbents (Organic Geochemistry, 2006, Vol. 37, 321-333). Most of these studies have sought to use the natural cellular structure of the plant tissue and the porous nature of the cell wall, which is enhanced during carbonization. However, no research has been conducted to produce carbon materials making use of the nanometer scale arrangement of plant cell wall components.